Fig. 299.
If we increase the angle from 45° to 60°, then the reflection of the plane and cube will lean backwards as shown in Fig. 300. If we place it on a level with the original plane, the cube will be standing upright twice the distance away. If the mirror is still farther tilted till it makes an angle of 135° as at E (Fig. 298), or 45° on the other side of the vertical Oc, then the plane and cube would disappear, and objects exactly over that plane, such as the ceiling, would come into view.
In Fig. 300 the mirror is at 60° to the plane mn, and the plane itself at about 15° to the plane an (so that here we are using angular perspective, V being the accessible vanishing point). The reflection of the plane and cube is seen leaning back at an
angle of 60°. Note the way the reflection of this cube is found by the dotted lines on the plane, on the surface of the mirror, and also on the reflection.
Fig. 300.